Materials Performance

SEP 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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Page 94 of 128

36 SEPTEMBER 2018 W W W.MATERIALSPERFORMANCE.COM
COATINGS & LININGS ESSENTIALS
Continued f rom page 35
temperatures up to 1,100 °F (593 °C). e
poly siloxane hybrid chemistry still con-
tained a densely cross-linked organic poly-
meric structure. In cyclic ambient-hot-
ambient service on small-diameter piping
or convoluted small shapes, this first-
generation polysiloxane coating tended to
crack and disbond from the substrate due
to internal stresses caused by the inherent
two-component, highly cross-linked hybrid
chemistry. In the intervening two decades,
this poly siloxane has continued in ambient
temperature service, but is rarely used on
high-heat equipment.
During the last 15 years, inorganic
copolymer (IC) and inert multipolymeric
matrix (IMM) coatings have been widely
used for CUI mitigation. Reynolds and Bock
explain that these coatings, which cure at
temperatures between 300 to 360 °F (~150
to 180 °C), fall into the category of second-
generation polysiloxanes. For these coating
chemistries, the surface temperature limits
are normally in the region of 1,200 °F (649
°C). e higher level of temperature toler-
ance is mainly due to the elimination of
organic counterparts, the high concentra-
tion of inorganic siloxane-based polymers,
and higher flexibility.
e introduction of the second-genera-
tion polysiloxane coatings was a step for-
ward for providing protection to substrates
under insulation; however, there are issues
with the coatings' usage in the field, such as
a soft film before they are heated to curing
temperatures. e necessary heating step
not only affects the mechanical properties
of the coating but also corrosion, UV, and
chemical resistance, as well as adhesion—
all of which are required to ensure maxi-
mum CUI protection. Multiple failures have
been identified in the field, either before
service temperatures reach >300 °F or dur-
ing use below curing temperatures.
Now, a third-generation polysiloxane for
CUI mitigation is available. Launched in
2015, this coating is a single-component,
fully ambient-temperature cure, inorganic
polysiloxane. Developed and tested under
multiple laboratory and field test protocols,
the third-generation polysiloxane elimi-
nates the field issues experienced with the
second-generation polysiloxane coatings,
including decreased film hardness, anticor-
rosion properties, and weathering resis-
tance prior to post-application curing. For
example, Reynolds and Bock explain,
removing the heating requirement to obtain
properties for CUI protection, which is nec-
essary for the second-generation coatings,
facilitates full protection in ambient appli-
cation temperatures as low as 50 °F (10 °C)
and specification temperatures that range
from –320 to 1,200 °F (–196 to 650 °C).
Additionally, they comment, a new liq-
uid-applied thermal insulation coating
(TIC) was commercialized in early 2017.
TICs have been used for more than 10 years
in a range of different applications includ-
ing thermal insulation and personnel pro-
tection. e low thermal conductivity (λ)
properties of the coatings reduce the hot or
cold surface temperatures of processing